1. Field of the Invention
The present invention relates generally to a filter press frame and, more particularly, to a lightweight, non-corrosive, filter press frame generally comprising head, tail, follower, side band and legs typically operable for compressing a plurality of filter elements.
2. Description of the Background
Filter presses have been used for over a century to separate liquids from solids. Yet to a large extent, today's filter press frames use the same technology that was used one hundred years ago. Today's filter presses also have the same corresponding problems that have plagued filter presses for the last century.
This is not to say that filter presses are not the most efficient means to perform certain widespread processing functions. Filter presses are quite effective and economical for the job they are intended to perform. Therefore, filter presses are used in many different processes.
During the last century, filter presses have found and continue to find wide and increasing use both in manufacturing processing and in ecological maintenance such as waste treatment. An incomplete list of filter press manufacturing process usage today includes manufacturing of pigment and dyestuff, pulp and paper, wine and beer, mining processes and production of precious metals, ceramics production, production of food colors and many food products, pharmaceuticals, chemical processing, silicone fluids, oil field brine filtration, sugar syrups, protein extraction, and the like. Filter presses process waste including metal and plastic waste treatment, plating waste recovery, ferrous and non-ferrous foundry waste, steel mill waste, printed circuit board waste, tannery waste, fiberglass production wastes, metal tubing part tumbling wastes, municipal wastes, lime softening, offshore oil well drilling fluid wastes. Filter presses are found in lumber treatment plants, power oil refineries and petrochemical plants, power plants, shipyards, food production plants, storage terminals, retention ponds, shipyards, boiler plants, and other plants related to the products listed above.
In operation, a filter press applies a large force to a stack of filters to thereby seal, pressurize, and squeeze the fluid within the filter press system through each filter. The fluids used with filter presses are often reactive bases or acids. The forces required to seal the stack of filters with the liquid therein under pressure is typically in the tens of thousands of pounds or more. For this reason, despite the problems associated therewith, filter presses have required and used a massive iron frame for the last century. The iron frame is very heavy, requires significant expensive machining operations to manufacture, and requires extensive maintenance such as sanding and painting to avoid damage by caustic/acidic/corrosive fluids. Thus, the costs of maintenance, the costs of transportation, and operation, as well as the costs of making of filter press frames is high. Stainless steel is sometimes used for making filter presses used but has never been a completely satisfactory substitute. Stainless steel is more expensive than iron, is just as heavy, and does not always prevent corrosion.
Representative patents to problems related to filter presses, filter press frames, and operation of filter presses include the following:
U.S. Pat. No. 4,500,379, issued Feb. 19, 1985, to Ford et al., discloses a composite fiber reinforced plastic frame having a core material at least partially formed from the continuous wrapping of roved layers of glass fiber impregnated with a catalyzed thermosetting resin within a corrosion resistant liner and having reinforced comers. This type of filter press is not the type of filter press concerned with this application and does not have a head, tail, follower, side band and other components for pressuring a stack of filter plates. Instead, this type of filter press carries electrodes on each side of the frame and operates by chemical reaction when voltage is applied to the electrodes, rather than by application of a physical pressure on a fluid to force the fluid through one or more filter elements. Filter presses of the bipolar membrane cell type have long been constructed of heavy plastic, which has long been a suitable material for the relatively very light physical loads.
U.S. Pat. No. 4,155,830 issued May 22, 1979, to Sukhobrusov et al., discloses a filter press including a support plate and a pressure plate and a set of chamber-type filter plates arranged therebetween. Each filter plate is provided with a cloth filtering barrier in the form of an endless belt which is supported by two rollers fastened to two opposite walls of the filter plate in such a manner that both runs of the belt extend on the side of a draining barrier of the filter plate.
U.S. Pat. No. 5,482,623, issued Jan. 9, 1996, to H. G. W. Pierson, discloses a plurality of substantially parallel filter plates assembled as a unit and locatable within a substantially rigid outer shell to provide a closed vessel. Either or both of the unit and the shell are movable relative to the other between a position wherein the unit is sealed within the shell to enable pressurized supply to the shell of the medium to be filtered via the plates and a position wherein the unit is at least partially removed from the shell to enable discharge of resultant filter cake from the plates. A substantially flexible membrane is provided as a lining to the shell so that a space between the lining and the shell is inflatable by pressure medium.
U.S. Pat. No. 3,926,811, issued Dec. 16, 1975, to W. Ramsteck, discloses a pair of geometrically identical filter plates lying one against the other which are each formed with a rigid central panel and a rigid frame surrounding the panel. A flexible web interconnects the outer edge of the rigid panel and the inner edge of the frame so as to allow this panel to be displaced by fluid pressure between the panels so as to press a filter cake.
U.S. Pat. No. 4,166,035, issued Aug. 28, 1979, to W. Ramsteck, discloses a filter plate assembly for a filter press with a substantially rigid support plate against which bears a filter plate. This filter plate is integrally formed of elastically deformable material and has an annular outer frame which lies against the support plate and defines a frame plane.
U.S. Pat. No. 4,508,623, issued Apr. 2, 1985, to Heckl et al., discloses a filter plate assembly which has a substantially rigid support plate having a face formed of a central region and an outer periphery bounding the region, a substantially rigid annular frame having a annular face at least closely confronting the support plate face at the periphery, and a generally planar and elastically deformable central filter panel formed integrally with the frame and engageable with the central region with the periphery.
A review of the above patents shows that there remains a need for a lightweight, corrosion resistant filter plate frame assembly that offers dependable operation at reduced levels of capital investment. Those skilled in the art have long sought and will appreciate the present invention which addresses these and other problems.